In a copper vapor laser ground state (.sup.2 S.sub.1/2) copper atoms are pumped by direct electron impact into first resonant states (.sup.2 P.sub.3/2 and .sup.2 P.sub.1/2). Stimulated emission can then occur between these resonant states and the two lower metastable states (.sup.2 D.sub.3/2 and .sup.2 D.sub.5/2). The resulting emission is at two visible wave lengths, 5106 A (.sup.2 P.sub.3/2.fwdarw..sup.2 D.sub.5/2) and 5782 A (.sup.2 P.sub.1/2 .fwdarw..sup.2 D.sub.3/2). In order to achieve a population inversion between the resonant and metastable states, laser amplifier pumping must be fast, because of short resonant life times, and the metastable population density must be low. Fast pumping is achieved with low induction pulsed discharge circuits. Typical discharge characteristics are, (a) initial rates of current rise of the order of 10.sup.10 amperes per second, and (b) current pulse widths of the order of 100 nanoseconds.
The metastable population density increases during each current pulse and decays between current pulses. It is this decay rate that determines the minimum allowed time between pulses and hence the maximum allowed pulse repetition rate of the laser. The level to which the metastable population density decays can be no lower than the equilibrium value determined by the copper vapor temperature. It is theorized that if the copper vapor temperature is allowed to exceed 3000.degree. K., the equilibrium metastable population density will be too high and the population inversion will not occur.
The copper vapor laser has a demonstrated efficiency of about 1%. Hence about 100 times the extracted optical energy is deposited in a lasant-buffer gas mixture with each pulse and this energy or waste heat must be removed while assuring that the lasant temperature does not exceed about 3000.degree. K.
Experiments to date on copper halide lasers have been conducted in relatively small bore tubes where the tube wall plays a dominant role in removing waste heat. The small volume of these tubes has limited the average power to the order of 10 watts. By using an oscillator and several amplifiers, this power could probably be increased by a factor of 10. In order to make large increases in average output power, however, amplifiers with large cross-sectional areas would be required. Extracting the waste heat, while maintaining the lasant at or below about 3000.degree. K., and providing fast uniform discharges has become a major challenge.
The present invention provides a means for solving the above problem by flowing a copper vapor and buffer gas through a laser amplifier at a rate just high enough to prevent overheating of the copper atoms. Heat is removed from the laser amplifier by convection, as the lasant-buffer gas mixture absorbs waste heat. Within the amplifier, the temperature will increase linearly from about 700.degree. K. at the amplifier entrance port to about 3000.degree. K. at the exit port. The 700.degree. K. entrance port temperature is determined by the required vapor pressure when copper chloride is the source of copper atoms.